EVAPORATIVE EMISSIONS: DEVELOPING AUSTRALIAN EMISSION ALGORITHMS Giorgos Mellios 1 , Robin Smit 2 and Leonidas Ntziachristos 3 1 EMISIA SA, Antoni Tritsi 21, GR 57001, Thessaloniki 2 Department of Science, Information Technology, Innovation and the Arts, Air Quality Sciences, Inventory, Modeling and Assessment Unit, Brisbane, Australia 3 Lab of Applied Thermodynamics, Aristotle University, GR 54124, Thessaloniki, Greece Abstract Evaporative emissions from motor vehicles contribute significantly to hydrocarbon emissions in urban areas. This contribution is typically in the order of 10-25% of total HC emissions from road transport, but contributions up to about 60% have been reported. Given the importance of hydrocarbon emissions for modelling of photochemical smog and secondary particles, as well as quantification of the levels of exposure to specific hydrocarbons (benzene, toluene, etc.), accurate estimation of evaporative emissions is vital. This paper discusses the development of emission algorithms from Australian and European test data, which have been incorporated in the COPERT Australia software program. Differences between Australian and European technologies (canister size, fuel tank size, etc.) are discussed. The algorithms are then used to estimate total evaporative emission loads for Queensland and these estimates are compared to predictions for other types of emissions (hot running, cold start). Keywords: evaporative emission, motor vehicles, diurnal losses, activated carbon canister 1. Introduction The term ‘evaporative emissions’ refers to the sum of all fuel-related non-methane volatile organic compounds (NMVOC) emissions not derived from fuel combustion. Breathing losses through the tank vent and fuel permeation are in general the most important sources of evaporative emissions in a vehicle. Breathing losses are due to evaporation of petrol in the fuel tank during driving and parking as a result of normal diurnal temperature variation. In current vehicles vapour emissions are controlled by means of an activated carbon canister connected to the fuel tank. Various studies (CRC 2004, Reuter et al 1994) indicate that fuel permeation through the plastic and rubber components of the fuel and vapour control system contribute significantly to the total evaporative emissions. There are three main mechanisms causing evaporative emissions from gasoline powered vehicles. • Diurnal losses are associated with the daily (diurnal) variation in ambient temperature and result from the vapour expansion inside the gasoline tank that occurs as the ambient temperature rises during the daylight hours. • Hot soak emissions occur when a hot engine is turned off and heat from the engine and exhaust system increases the temperature in the fuel system. • Running losses are the result of vapour generated in petrol tanks during vehicle operation. Evaporative emissions can have a significant contribution to total NMVOC emissions from road transport, especially at high ambient temperatures and when high volatility fuels are used (e.g. petrol – ethanol blends). Therefore, it is essential to use accurate evaporative emission factors for Australian conditions. Empirical Australian vehicle emissions data have therefore been analysed and used in this research to develop appropriate evaporative emission factors. Coupled with a well-established method already used in Europe (EEA, 2009), these emission factors have been incorporated in the COPERT Australia software (Emisia, 2013).